Definition

Chorionic villus sampling is a test that is done for pregnant women. It involves removing chorionic villi from the placenta. The placenta is the organ that provides nutrients and oxygen to the baby during pregnancy. It also removes waste from the baby’s blood. Chorionic villi is the tissue that makes up most of the placenta. The test is done during the 9th-13th weeks of pregnancy.

Reasons for Test

Chorionic villi contains valuable information about the baby’s genes. By testing chorionic villi, the doctor can find out if the baby has a chromosomal abnormality, like
Down syndrome
. The test can also detect genetic disorders, like
cystic fibrosis
. It cannot detect neural tube defects, such as
spina bifida
.

You and your doctor may consider this test if you have:

Other tests, such as a first trimester
ultrasound
, with abnormal results

Previous pregnancy with a chromosomal abnormality

Advanced maternal age: 35 years old or older

You or your partner is a carrier for a genetic disorder

Family history of a genetic disorder

Although a test showing a healthy baby without a genetic disorder is ideal, you will need to be prepared if the results show otherwise. If the test shows that your baby may have a genetic disorder, it may require you to make tough decisions regarding your pregnancy, such as whether or not to continue it. If you do continue with the pregnancy, you will need to address concerns, such as planning for a child with special needs. Your doctor can help you understand the pros and cons of having this test, as well as talk to you about options once you know the results.

What to Expect

Prior to Test

Since you may need to have a full bladder, drink plenty of fluids before the test. However, depending on how your placenta is positioned, you may be asked to urinate before the test. Talk with your doctor about specific ways to prepare for the test. Also, arrange to have someone drive you home from the hospital.

Description of Test

The doctor will use an ultrasound to find out the position of your placenta and your baby’s age. An ultrasound uses sound waves to create images of organs or tissue inside the body.

The doctor will cleanse your abdomen with antiseptic. Using the ultrasound images as a guide, she will insert a long, thin needle through your abdominal wall. The needle will enter your uterus, avoiding the baby. You may feel cramping at this time. A tissue sample from your placenta will be withdrawn into a syringe through the needle.

After Test

The doctor may want to monitor your baby’s heart rate using an ultrasound. You will be encouraged to rest once you are home. You will most likely be able to return to normal activities the next day.

How Long Will It Take?

30-45 minutes

Will It Hurt?

You may feel some cramping during and after the test. You may also have a small amount of bleeding right after the test.

Results

It may take 1-2 weeks to receive your test results. You will go over your results with your doctor or a genetic counselor.

If the test results are unclear, you may need to have another test called an
amniocentesis
. This is to help get a better understanding of the results.

If the results show that your baby has a genetic disorder or problems with the chromosomes, you and your doctor will discuss how to manage your pregnancy. This may be a stressful time. Seeking support from your family, friends, and healthcare team can help.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY.
Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.